Theme session G

Marine foodwebs from end-to-end and back again, a theme session in honor of John Steele

Tuesday 19 September, 14:30–16:00 & 16:30–18:00

Room: Grand ballroom E

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​​​​​​With his seminal monograph, "The Structure of Marine Ecosystems", John Steele pioneered the application of network models to marine foodwebs. Since then, end-to-end (E2E) models have been constructed for hundreds of marine ecosystems around the world. These include models that include only some foodweb components as well as those that cover primary production to top predators.

Originally formulated to understand the structure, linkages, and energy flow through marine foodwebs, E2E models are now being used to address a range of applied questions. Coupled with satellite-derived estimates of primary production, the models are being used to estimate potential fisheries production at a global scale. Conversely, top-down models ask how much and what type of prey are needed to support top predators and fisheries. Scenarios are run to reconstruct past foodwebs prior to human exploitation, and future foodwebs under changing climate conditions. As Steele first showed, dynamic E2E models can be constructed as systems of coupled differential equations. These models are being used to investigate harvest strategies, including balanced harvesting. The role of physical forcing in structuring marine foodwebs has been investigated by incorporating imports and exports at different trophic levels.

Foodweb models of higher trophic levels have been coupled with biophysical circulation models, allowing a more realistic accounting of spatial dynamics. Despite these successes, a number of challenges remain, including statistical parameter estimation, and the application of E2E models to strategic decision-making.

The major aims of this session are to recognize John Steele’s contributions to ICES and his impact of the field of marine ecology. During his long and productive career, John continued to work on what have variously been called energy budgets, foodweb, network, or end-to-end models. Specific objectives are to showcase the state of the art in E2E modeling and to trace their development from Steele's pioneering work.